1. Field of the Invention
The present invention relates to an outboard engine with a blow-by gas returning apparatus positioned in such a manner as to make good use of space to thereby render the engine compact in construction.
2. Description of the Related Art
A breather apparatus for a vertical outboard engine is known from, for example, Japanese Patent Laid-Open Publication No. HEI 5-149124 entitled "BREATHER APPARATUS FOR VERTICAL FOUR-STROKE ENGINE". The disclosed breather apparatus is comprised of a head breather chamber forming a first breather chamber disposed on an outer surface of an engine head cover, PCV (positive crankcase ventilation) hose extending from the head breather chamber to a surge tank located downstream of a throttle body, a crank breather chamber forming a second breather chamber disposed on an outer surface of a crankcase, and a blow-by hose extending from the crank breather chamber to a flow control pipe located upstream of the throttle body.
The breather chamber of the breather apparatus takes the form of a maze to have a large capacity so that an engine oil contained in a blow-by gas can be effectively separated from the blow-by gas. The breather apparatus also enables efficient exchange between the blow-by gas in a crank chamber and fresh air during a part-load operation of the engine.
However, in the breather apparatus, the head breather chamber is provided in the head cover while the crank breather chamber is provided in the crank case. That is, since it has the breather chambers provided at both ends thereof, the engine is elongated axially of the cylinders, thus occupying a large space of the outboard engine. Moreover, provision of the breather chambers at both ends of the engine causes the center of gravity of the engine to be displaced outwardly, thus resulting in imbalanced mounting of the outboard engine to a boat.